Volumetric Analysis

Question 1

What is a Volumetric Analysis?

Answer 1

Quantitative Technique
Involves measuring volume of a solution with a known concentration which is used to determine the concentration of the analyte.

Question 2

What process is involved in a volumetric analysis?

Answer 2

Titration

Question 3

Steps to a Volumetric Analysis

Answer 3

1. Preparation of standard solution
2. Titration between standard solution and solution to be standardised
3. Titration between standardised solution and analyte
4. Calculations to determine analyte concentration

Question 4

Volumetric Flask

Answer 4

Used to prepare standard solution
A fixed volume usually 100mL or 250mL

Question 5

Pipette

Answer 5

Used to transfer a known volume of solution being analyzed to the conical flask
Fixed volume, commonly 20 - 25mL

Question 6

Aliquot

Answer 6

an amount taken from a larger quantity, so that it can be tested

Question 7

Burette

Answer 7

A variable volume
Holds up to 50mL
Contains the standard solution

Question 8

Titre

Answer 8

the volume of a solution required to complete a reaction in a titration.

Question 9

Conical Flask

Answer 9

Used for holding the aliquot delivered by the pipette

Question 10

What is a standard solution?

Answer 10

Concentration is accurately known, prepared in volumetric flask, prepared using a primary standard

Question 11

Requirements of a primary standard

Answer 11

• available in pure form
• known formula
• stable enough to not react with the atmosphere
• soluble in water
• high molar mass

Question 12

Standardization

Answer 12

A standard solution can be used to standardise another solution

Question 13

Titration

Answer 13

adding one solution to another until a reaction is complete

Question 14

Indicator

Answer 14

signals the point where neutralisation reaction is complete

Question 15

Equivalence point

Answer 15

reaction is complete according to mole ratios in equation

Question 16

Endpoint

Answer 16

when the indicator changes colour

Question 17

Factors to consider when choosing an indicator

Answer 17

End point of the indicator must be close to the equivalence point of the reaction

Question 18

What does CONCORDANT mean?

Answer 18

0.10mL between the lowest and highest titre

Question 19

Why should we use concordant titres?

Answer 19

Increases reliability and precision of results, minimizing effects of random errors

Question 20

STRONG ACIDS

Answer 20

HCl, NO3, H2SO4

Question 21

WEAK ACIDS

Answer 21

Carboxylic acids

Question 22

STRONG BASES

Answer 22

NaOH, KOH, Ba(OH)2

Question 23

WEAK BASES

Answer 23

NH3

Question 24

What are TITRATION CURVES?

Answer 24

Graph of Burette Volume versus pH in the titration flask

Question 25

What are the types of experimental errors in a volumetric analysis?

Answer 25

1. Rinsing Errors 2. Indicator Errors

Question 26

What are rinsing errors?

Answer 26

Lead to either overestimations or underestimations of analyte concentration Effects size of the titre delivered

Question 27

What should the volumetric flask be rinsed with?

Answer 27

Distilled Water

Question 28

What should the pipette be rinsed with?

Answer 28

The solution it is to contain

Question 29

Why shouldn't we rinse the pipette with water?

Answer 29

- decrease the concentration of solution in the pipette - hence a smaller titre of would be delivered by the burette to react completely - leading to a lower calculated concentration (underestimation)

Question 30

Why shouldn't we rinse the pipette with a more concentrated solution?

Answer 30

- Increase the concentration of solution in the pipette - Larger titre required to react completely - Higher calculated concentration (overestimation)

Question 31

What should the burette be rinsed with?

Answer 31

With the solution it is to contain

Question 32

Why shouldn't the burette be rinsed with water?

Answer 32

- dilute the concentration of solution in burette - larger titre required to react completely - higher calculated concentration of analyte

Question 33

Why shouldn't the burette be rinsed with a more concentrated solution?

Answer 33

- increase the concentration of solution in the burette - smaller titre required to react completely - lower calculated concentration of analyte

Question 34

What should the conical flask be rinsed with?

Answer 34

Distilled water

Question 35

Why shouldn't you rinse the conical flask with the solution it is to contain?

Answer 35

- Increases the concentration of solution - Greater titre required - Overestimation

Question 36

Poor Indicator Choice

Answer 36

Incorrect indicator choice can lead to overestimations and underestimations of final concentration

Question 37

Missed Indicator Endpoint

Answer 37

If titration is stopped after endpoint, the size of the titre will be bigger than it should be